Poly(ethylene glycol) Vesicles: Self-Assembled Site for Luminescence Generation

Abstract

Fluorescence in poly(ethylene glycol) (PEGs 400-12000) solutions is reported here for the first time. PEG solutions form a vesicular organization with the hydrophilic groups attached at both ends which arrange themselves beyond a particular concentration and offer electron-dense regions at the center of the vesicle. These vesicles provide an inherent site for fluorescence generation in PEG solutions. Fluorescence emission was observed at ~380 nm with an excitation wavelength of 300 nm. PEG of molecular weight 6000 was found to show maximum emission intensity at a particular concentration. The formation of PEG vesicles (~1 nm size) was confirmed by dynamic light scattering (DLS) and confocal laser microscopy. On addition of metal ions the polymeric vesicle breaks up to monomeric PEG, and hence, the fluorescence intensity decreases with a red shift. Fluorescence lifetime measurements indicate the nature of complexation of the metals with PEG. Since PEGs are used as one of the phases in aqueous biphasic systems (ABS) of liquid-liquid extractions, the nature of the fluorescence emission spectrum of the PEG phase after extraction was studied. Metal extraction in the PEG-rich phase of an ABS leads to quenching of fluorescence in PEG.

Block copolymer as a novel functional phase in an aqueous biphasic system for species selective iodine extraction

“…Conductance measurements were performed to nd the critical micellar concentration. 27 Fig. 1 shows the emission spectra of copolymer solutions which show a gradual increase in intensity with increasing concentrations.…”

“…The observed conductance values are very low (in the mS range) as the conductance arises due to polar head groups and not by the actual ions. 27 Micellar aggregation results in the formation of electron dense regions in solution which accounts for the observed increase in conductance. Dynamic light scattering experiment reveals that the hydrodynamic radius of the micelles lies in 1-2 nm range (Fig.…”

“…This brown color indicates charge transfer complex formation between iodine and the polymeric entity which is also in agreement with earlier observations. 27 As iodine is an electron acceptor, it can easily accept lone pair of electrons from oxygen atoms of the copolymer resulting in complexation; this type of complexation was used to determine CMC value of nonionic surfactants by several researchers. [30][31][32] In fact, the tendency of the otherwise water insoluble I 2 to dissolve in PPG-PEG-PPG is partially attributed to this aforesaid complexation.…”

Fluorescence Behavior and Mechanisms of Poly(ethylene glycol) and Their Applications in Fe3+ and Cr6+ Detections, Data Encryption, and Cell Imaging

“…It is to note that, among all these reported studies, the luminescence property of PEG is rarely available. ,,,,, PEG chains, and its triblock copolymer, i.e., PEG–poly­(propylene glycol)–PEG, have been deemed as nonemissive. ,, To make this triblock polymer emissive, chemical modifications were conducted by attachment of amino groups to its chain ends, followed by amidation by palmitic acid. The polymer chains are therefore turned amphiphilic and may self-assemble to form micelles, whereas the amide groups served to form multiple intramolecular hydrogen bonds and to restrict the chain motions, leading to the anticipated fluorescence through the CTE principle. , In fact, in the very few studies focusing on the fluorescent property of PEG, very feeble emission was reported on aqueous PEG solution, even at relatively high concentrations, i.e., 50 mg/mL, and up to 50–60% . Under such high concentrations, the highest emission intensity was around 800 (a.u.…”

Competent arsenicals: aqueous biphasic extractions and their application in nitrate/nitrite speciation

“…This is possibly due to the micellar arrangement of 50% PEG solution. 21 In direct PEG solution, the charged arsenomolybdenum blue species remains at the intermicellar space which is easily available to the nitrites having higher oxidizing ability than nitrates. Thus the rates of decay in presence of nitrate is very small (10 À5 s À1 ) (Fig.…”