Pure water pyrene

Pyrene was used as a fluorescent probe to sense various hydrophobic sites in the microheterogeneous architecture offered by PAMAM dendrimers, possessing an ammonia core and sodium carboxylated surface (Gn.5, n = 0-9) [17]. The IJIi ratio of pyrene in the presence of low generations (G0.5-G3.5) remained very similar to those in pure water. In the presence of higher generation dendrimers, however, pyrene sensed a more hydrophobic outer surface which was presum-... 

Figure 4.3.4 Stern-Volmer type curve for pyrene fluorescence signal decrease upon increasing the concentration of Suwannee river humic acid in pure water (initial pH 6.5). (From Algarra et al. (2005), with kind permission from Springer Science and Business Media)...

Figure 5. The dependence of the rate of proton dissociation from excited 8-hydroxy-pyrene- 1,3,6-trisulfonate on the mole fraction of ethanol in water, and the respective proton conductivity of the mixtures. The rate of proton dissociation was measured by time resolved ( ) or steady-state ( ) fluorescence. The proton conductivity of the solutions (A) is normalized for pure water conductivity. Data taken from Erdey-Grutz and Lengyel (1977).

Soon after the introduction of convergent dendrimer synthesis, " hemispherical, aryl-ester-coated, benzyl ether-based dendrons were reported. Attachment to a divalent core and conversion to the polycarboxylate 25 (Fig. 5) yielded dendriiners that facilitated a 200-fold increase in pyrene (26) solubility in water eompared with that of pure water without the dendrimer. Notably, use of sodium dodecyl sulfate (SDS above cmc 9 X 10 M) for pyrene encapsulation resulted in only an 100-fold enhancement. 

More quantitatively, we plot the normalized concentration (Cpy,s/Cpy,w) of solubilized pyrene against polymer concentration in Fig. 5.33a, where Cpy,s and Cpy,w represent the measured pyrene concentration in micellar solution and the saturated concentration in pure water, respectively. As shown in Fig. 5.33a, Cpys/Cpy, linearly increases with polymer concentration for all HB-(PAA) -g-(PS) +i copolymers with different n values. Moreover (Cpy,s/Cpy,w) =i > (Cpy,s/Cpy,w) =io > (Cpy,s/Cpy,w)n=47, indicating the solubilization efficiency of HB-(PAA) -g-(PS) +i copolymers decreases with the size or branching degree of hyperbranched PAA core for a given polymer concentration. As we know, pyrene molecules mainly... 

Fig. 5.33 a Polymer concentration and b styrene component concentration ofHB-(PAA) -g-(PS) +i copolymers dependence of py,s l py,w. where Cpy s and Cpy,w represent the dissolved pyrene concentration in micellar solution and pure water, respectively... 

In Fig. 4.3 two emission spectra of pyrene in a solution of a modified polymer (10 unit moll" of 3-C12) are given. One of them (full line) is obtained in low ionic strength solution (0.1% NaCl) and the ratio /1//3 is found to be significantly the same as that in pure water, i.e. 1.85, indicating no formation of hydrophobic aggregates. When the ionic strength is very high (10% NaCl) the intensity of the third peak increases (dashed line in Fig. 4.3) and the value is... 

At salt concentrations lower than the the value of /1//3 depends on the nature of the modified polymer. For the polymer 3-C12 this value is very close to that measured in pure water, but decreases slightly for the 3-C14 and significantly for the 3-C18. It seems that the pyrene experiences a more hydro-phobic environment even before the onset of the hydrophobic aggregation. One can ascribe this result to the fact that the hydrophobic pyrene probe lies preferably close to the nonpolar alkyl chain than in the bulk solution. 

The ratio of the third to the first vibronic bands (h/Ii) in pyrene fluorescence spectra depends on the polarity in the microenvironments where pyrene exists [27] 7,// values being larger in less polar media. A small-molecular model compound, PyPAm in Scheme 3, which possesses a substituent group similar to the Py label in the polymers, shows an /V/i ratio of 0.59 in aqueous solution, reflecting the polarity of water [28]. The copolymer of AMPS and PyMAm [poly(A/Py) see Scheme 3], a reference polymer for comparison, exhibits the same / //i ratio as that PyMAm in water [29], indicating that the Py labels are exposed to the aqueous phase because the reference copolymer assumes an extended conformation in pure water. In contrast, pyrene-labeled amphiphilic terpolymers poly(A/La/Py), poly(A/Cd/Py), and poly(A/Ad/Py) (see Scheme 3) shows /V/i ratios of 0.80, 0.83, and 0.76, respectively, all larger than that of the reference copolymer. This is an indication that the Py labels are buried in the hydrophobic microdomains in the unimer micelles in aqueous solution [22]. 

Dunn and Stich [78] and Dunn [79] have described a monitoring procedure for polyaromatic hydrocarbons, particularly benzo[a]pyrene in marine sediments. The procedures involve extraction and purification of hydrocarbon fractions from the sediments and determination of compounds by thin layer chromatography and fluorometry, or gas chromatography. In this procedure, the sediment was refluxed with ethanolic potassium hydroxide, then filtered and the filtrate extracted with isooctane. The isooctane extract was cleaned up on a florisil column, then the polyaromatic hydrocarbons were extracted from the isoactive extract with pure dimethyl sulphoxide. The latter phase was contacted with water, then extracted with isooctane to recover polyaromatic hydrocarbons. The overall recovery of polyaromatic hydrocarbons in this extract by fluorescence spectroscopy was 50-70%. 

Chemicals. Antipyrine, carbon monoxide (Matheson, Coleman and Bell, Los Angeles, CA), and 1 CH3-N-antipyrine (11.1 mCi/mM, ICN, Irvine, CA) were purchased. Aldrin (1,8,9,10,11,11-hexa-chloro-2,3-7,6-endo-2,1-7,8-exo-tetracyclo (6.2.1.13,6.02 7) dodeca-A,9-diene) and its epoxide, dieldrin were gifts of Shell Development Co. (Modesto, CA). Each was recrystallized from methanol-water solutions and was greater than 99% pure as determined by gas chromatography. l CH30-p-Nitroanisole (1.9 mCi/mmole) was synthesized (1A) and 3H-benzo(a)pyrene (8.3 Ci/ mmole) was purchased (Amersham-Searle Co., Arlington Heights,... 

A variety of aromatic hydrocarbons (often in large doses) have been used to induce MFO in mammalian systems and more recently in fish. 3-methylcholanthrene and benzo(a)pyrene are potent inducers in mammals and are also effective in fish (8, 14,15). Other agents as PCB (12,13) in contrast to DDT type compounds (13) have also been used to induce fish. We are not aware, however, of any studies where fish have been induced by pure hydrocarbons (or other compounds) dissolved or accommodated in water. 

Pyrene Carboxaldehyde Probe Studies. Fluorescence spectra of 1-pyrene carboxaldehyde in nonane solutions of sulfonates A and B and In an octane solution of Aerosol OT are compared to the probe spectra in pure hydrocarbon media in Figure 1. Parts (a) and (b) are of sulfonates A and B systems, respectively part (c) is of aerosol OT system. They were constructed at different gain settings and therefore the intensities shown for the individual system are not directly comparable. The fluorescence intensity of 1-pyrene carboxaldehyde in nonane alone is much weaker than in either the sulfonate A or sulfonate B solution. Aerosol OT containing solubilized H.O does not enhance the fluorescence intensity of 1-pyrene carboxardehyde as much as sulfonates A and B, but the band maximum is shifted as expected for this probe in a water-rich medium. 

PSt-fe-PEO block copolymers were suggested to form spherical micelles in water solution with a dense core composed of the insoluble PSt. Thus they possess a core of a pure PSt phase surrounded by a water-swollen corona of PEO chains. One anticipates that the properties of the corona resemble those of typical nonionic PEO-based emulsifiers. The core is much larger for block copolymer micelles leading to larger aggregation numbers. When traces of pyrene are added to these solutions, the pyrene penetrates the core phase. Several spectroscopic properties are changed upon transfer into the more hydrophobic environment. 

Figure 3. Fluorescence spectra excited by a dye laser at 389.2 nm in an r -heptane matrix at 15 K of an adsorption chromatography fraction from a coking plant water sample (left,) and of pure benzo[a]pyrene (right,). Note that the two spectra are virtually superimposable ( 1).

Monoclinic prismatic tablets from alcohol or by sublimation. da 1.271. Pure pyrene is colorless, the usual contaminant which gives it a yellow color is tetracene. Solid and solns have slight blue fluorescence, mp 156. bp 404. Absorption spectrum Clar. Ber. 69, 1677 (1936) Seshan, Proc, Indian Acad. ScL A3, 148 (1936). Fluorescence maxi, ma Sannie, Poremski, Bull. Soc. Chim. [5] 3, 1139 (1936). Inso in water fairly sol in organic solvents. 

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