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Laser properties of fluorescent brightening agents
August 1976
OPTICS COMMUNICATIONS
Volume 18, number 3
LASER PROPERTIES OF FLtJORESCENT
BRIGHTENING AGENTS
W. MAJEWSKI and J. KRASINSKI Institute of Experimental
Physics, University of Warsaw, Hoia 69, 00-681
Warsaw, Poland
Received 17 March 1976
The laser properties of 19 dyes commonly used as fluorescent brightening agents (FBA) have been studied. A nitrogen laser served as the pumping source The absorption spectra and the relationship between laser power and wavelength was determined for these dyes. Since several of these compounds have an efficiency comparable to that of the POPOP scintillator commonly used in this part of the spectrum, and since they are easily soluble in alcohols and furthermore, are very inexpensive, they may be competitive with other dyes hitherto used in the violet-blue region.
It is well known that some materials fluoresce strongly after ultraviolet excitation because of fluorescent brightening agents (FBA) added to the material itself during processing or because of traces of FBA contained in laundry soaps and detergents. Since FBA are efficient fluorescers having a high fluorescence efficiency, and since they are quite stable, we decided to study their laser properties. Of the 27 products studied, we obtained laser action in 19. Compounds used as FBA are quite different insofar as their chemical structure is concerned; all, however, fluorescence in the blue-violet region. The most frequent dye center is the -CH=CHbond. When the solubilizing group -S03Na is present in the molecule, these compounds are easily soluble in alcohols. Because they are mass produced, FBA are incomparably less expensive than conventional laser dyes. In compounds with similar structures except for the solubilizing groups, Kotzubanov et al. [ 11, Deutsch and Bass [2], and Furumoto and Ceccon [3] have obtained laser action. The experimental setup consisted of a tunable dye laser pumped by a 6 ns, 200 kW nitrogen laser with a repetition frequency of about 30 Hz. A glass prism was used to tune the dye laser in an arrangement similar to that described by Dunning et al. [4]. The average power of the dye laser was measured by means of a thermocouple. Solutions were prepared by dissolving FBA in appropriate solvents and filtering in order
to eliminate insoluble impurities which are inevitably present in a commercial product. Some of the most efficient dyes were purified chromatographically, which did not, however, seem to notably enhance their efficiency. Optimal concentrations were chosen for all measurements; usually these were somewhat less than 1 g/liter. Figs. la-o show the relationship of laser power to wavelength as well as absorption curves for the FBA studied. Fig. Ip depicts the same curves obtained for POPOP, the dye which is most commonly used and most efficient in this spectral region. Fig. 1 does not include results for the three least efficient FBA: Tinopal DMS, Blanbe1333 and Tinopal 2B which showed very weak laser properties at h = 43.5 nm. The power of the dye lasers is presented in arbitrary units with 1 .O corresponding to the maximum power obtained with POPOP in dioxane [5] . Because of patent secrets we were not able to find the structure of all of the FBA tested by us. These compounds are listed in the Colour Index in a separate category without their formulae. As an example, Tinopal BV is described in the Colour Index as FBA-I ; knowing the chemical structure of this compound we can identify it as CI 40630. As shown in figs. lb and le, brighteners Delft Weiss BSW, Uvitex CF and Weisstoner BV have an almost identical power and a somewhat broader tuning range than POPOP. The dye Blankophor R (fig. la) is comparable with a-NPO in toluene. 255
Volume
18, number
3
OPTICS COMMUNICATIONS
4
256
.
Fig. li.
Fig. lh.
47
in methanol
FBA
TINOPAL SS
1.2
1.4-
1.1
Fig. 1Q.
Fig. lj.
46
in
methanol
BLANKOPHOR BP FBA 116
FBA
TINOPAL RBS
absorption
Fig. In.
laser
NSI
r-
ir. methanol
UVITEX
Dependence of laser power and absorption on wavelength for the FBA studied. equal to 1.0 is the equivalent of the maximum power obtained from POPOP in dioxane.)
Figs. la-o.
I
1.2
14
Fig. Im.
Fig. lp. The same dependence
for POPOP in dioxane.
Fig. lp.
Fig. lo.
‘60
(The power
510
vqavelenqth [nm? 1p
Volume
18, number
3
OPTICS COMMUNICATIONS
In summary, we have determined that many compounds used a FBA have adequate laser properties. Because of their good efficiency, broad tuning spectrum, solubility in convenient solvents and low price, these compounds may well replace the organic scintillators which are at present most often used in this region.
1976
References [l]
[2] [3] [4]
The authors would like to express their gratitude to T. Wiech for his helpful suggestions.
August
[5]
V.D. Kotzubanov, Yu.V. Naboikin, L.A. Ogurtsova, A.P. Podgornyi and F.S. Pokrovskaya, Opt. Spectrosc. 25 (1968) 406. T.F. Deutsch, M. Bass, IEEE JQE QE-5 (1969) 260. H.W. Furumoto and H.L. Ceccon, IEEE JQE QE-6 (1970) 262. F.B. Dunning, R.F. Stebbings, G.K. Walters, R.D. Rundel Opt. Commun. 5 (1972) 267. F.B. Dunning and R.F. Stebbings, Opt. Commun. 11 (1974) 112.
259
OPTICS COMMUNICATIONS
Volume 18, number 3
LASER PROPERTIES OF FLtJORESCENT
BRIGHTENING AGENTS
W. MAJEWSKI and J. KRASINSKI Institute of Experimental
Physics, University of Warsaw, Hoia 69, 00-681
Warsaw, Poland
Received 17 March 1976
The laser properties of 19 dyes commonly used as fluorescent brightening agents (FBA) have been studied. A nitrogen laser served as the pumping source The absorption spectra and the relationship between laser power and wavelength was determined for these dyes. Since several of these compounds have an efficiency comparable to that of the POPOP scintillator commonly used in this part of the spectrum, and since they are easily soluble in alcohols and furthermore, are very inexpensive, they may be competitive with other dyes hitherto used in the violet-blue region.
It is well known that some materials fluoresce strongly after ultraviolet excitation because of fluorescent brightening agents (FBA) added to the material itself during processing or because of traces of FBA contained in laundry soaps and detergents. Since FBA are efficient fluorescers having a high fluorescence efficiency, and since they are quite stable, we decided to study their laser properties. Of the 27 products studied, we obtained laser action in 19. Compounds used as FBA are quite different insofar as their chemical structure is concerned; all, however, fluorescence in the blue-violet region. The most frequent dye center is the -CH=CHbond. When the solubilizing group -S03Na is present in the molecule, these compounds are easily soluble in alcohols. Because they are mass produced, FBA are incomparably less expensive than conventional laser dyes. In compounds with similar structures except for the solubilizing groups, Kotzubanov et al. [ 11, Deutsch and Bass [2], and Furumoto and Ceccon [3] have obtained laser action. The experimental setup consisted of a tunable dye laser pumped by a 6 ns, 200 kW nitrogen laser with a repetition frequency of about 30 Hz. A glass prism was used to tune the dye laser in an arrangement similar to that described by Dunning et al. [4]. The average power of the dye laser was measured by means of a thermocouple. Solutions were prepared by dissolving FBA in appropriate solvents and filtering in order
to eliminate insoluble impurities which are inevitably present in a commercial product. Some of the most efficient dyes were purified chromatographically, which did not, however, seem to notably enhance their efficiency. Optimal concentrations were chosen for all measurements; usually these were somewhat less than 1 g/liter. Figs. la-o show the relationship of laser power to wavelength as well as absorption curves for the FBA studied. Fig. Ip depicts the same curves obtained for POPOP, the dye which is most commonly used and most efficient in this spectral region. Fig. 1 does not include results for the three least efficient FBA: Tinopal DMS, Blanbe1333 and Tinopal 2B which showed very weak laser properties at h = 43.5 nm. The power of the dye lasers is presented in arbitrary units with 1 .O corresponding to the maximum power obtained with POPOP in dioxane [5] . Because of patent secrets we were not able to find the structure of all of the FBA tested by us. These compounds are listed in the Colour Index in a separate category without their formulae. As an example, Tinopal BV is described in the Colour Index as FBA-I ; knowing the chemical structure of this compound we can identify it as CI 40630. As shown in figs. lb and le, brighteners Delft Weiss BSW, Uvitex CF and Weisstoner BV have an almost identical power and a somewhat broader tuning range than POPOP. The dye Blankophor R (fig. la) is comparable with a-NPO in toluene. 255
Volume
18, number
3
OPTICS COMMUNICATIONS
4
256
.
Fig. li.
Fig. lh.
47
in methanol
FBA
TINOPAL SS
1.2
1.4-
1.1
Fig. 1Q.
Fig. lj.
46
in
methanol
BLANKOPHOR BP FBA 116
FBA
TINOPAL RBS
absorption
Fig. In.
laser
NSI
r-
ir. methanol
UVITEX
Dependence of laser power and absorption on wavelength for the FBA studied. equal to 1.0 is the equivalent of the maximum power obtained from POPOP in dioxane.)
Figs. la-o.
I
1.2
14
Fig. Im.
Fig. lp. The same dependence
for POPOP in dioxane.
Fig. lp.
Fig. lo.
‘60
(The power
510
vqavelenqth [nm? 1p
Volume
18, number
3
OPTICS COMMUNICATIONS
In summary, we have determined that many compounds used a FBA have adequate laser properties. Because of their good efficiency, broad tuning spectrum, solubility in convenient solvents and low price, these compounds may well replace the organic scintillators which are at present most often used in this region.
1976
References [l]
[2] [3] [4]
The authors would like to express their gratitude to T. Wiech for his helpful suggestions.
August
[5]
V.D. Kotzubanov, Yu.V. Naboikin, L.A. Ogurtsova, A.P. Podgornyi and F.S. Pokrovskaya, Opt. Spectrosc. 25 (1968) 406. T.F. Deutsch, M. Bass, IEEE JQE QE-5 (1969) 260. H.W. Furumoto and H.L. Ceccon, IEEE JQE QE-6 (1970) 262. F.B. Dunning, R.F. Stebbings, G.K. Walters, R.D. Rundel Opt. Commun. 5 (1972) 267. F.B. Dunning and R.F. Stebbings, Opt. Commun. 11 (1974) 112.
259